Electronic throttle control (ETC) systems are increasingly being utilized to control airflow into automotive engines to achieve improved vehicle emissions control, vehicle fuel efficiency, and vehicle drivability. In one such system, an engine torque request signal is generated based on a driver demand signal derived, for example, from the output of an accelerator pedal position sensor, perhaps in combination with a number of additional detected or inferred powertrain and/or vehicle operating parameters, and detected or inferred ambient conditions (such as intake air temperature and ambient humidity). A throttle plate in the engine's air intake, as well as perhaps a variation in the engine's nominal intake valve timing, are then controlled in response to the resulting torque request signal to thereby control airflow into the engine and the resulting generated torque output.
In order to improve vehicle drivability and reduce vehicle NVH, known ETC systems advantageously filter or “smooth” the generated torque request signal during demand signal transitions, particularly when the driver “lets up” on the accelerator pedal to thereby rapidly reduce the driver demand signal as sensed by a pedal position sensor (PPS) to a minimum value (also known as throttle “tip-out” and “close pedal”), to obtain a filtered requested torque signal that drops more slowly and ultimately blends into a corresponding minimum torque request. While such requested torque filtering can be particularly advantageous when the engine is coupled to a manual transmission, for example, to avoid generating undesirable drivetrain “clunk” due to mechanical lash within the drivetrain in response to abrupt requested torque transitions, this filtering technique can cause an unintended (upward) engine speed flare if the manual transmission is also being declutched during this filtered requested torque transition.